The present invention relates to a method and apparatus for coating with a gelatinizer an object having a growth ability such as a seed, a cell piece or the like having a germinating or rooting ability, and more particularly to a gel coating method and apparatus also capable of gel-coating a heavy seed or a seed having a poor germinating ability.
Conventionally, a coated object obtained by coating such an object to be sealed as a seed, a cell piece or the like with a macromolecular gel containing nutriments, medicament and the like and being elastic (hereinafter generically, the object to be sealed is called a xe2x80x9cseedxe2x80x9d and the coated object is called a xe2x80x9ccoated seedxe2x80x9d; and that is, hereinafter in case of referring to a xe2x80x9cseedxe2x80x9d or a xe2x80x9ccoated seedxe2x80x9d, the xe2x80x9cseedxe2x80x9d means not only a seed but also any object having a growth ability such as a cell piece having a germinating or rooting ability) is known. The coated seed has many advantages such as that the coated seed is effective to protect the seed from being eaten by animals or sterilize the seed, that it makes it easy to handle the seed by making the seed larger in grain diameter and thereby makes its seeding operation more efficient, and that furthermore it enables to improve its germination rate due to absorbing nutriments in the macromolecular gel.
By the way, as a typical method for automatically manufacturing above-mentioned coated seed, there are a double-cylinder nozzle method and a mold method.
First, a double-cylinder nozzle method is explained with reference to FIG. 7. This method slightly pressurizes the inside of a gel accommodating portion 3 of a gel accommodating block 2 into which a gelatinizer is supplied from a gelatinizer tank, not shown, by means of an air cylinder, not shown, fills a passage 4 of the gel accommodating portion 3 and a space 5 communicating with the passage 4 with the gelatinizer as well as raises the pressure inside the space 5, and thereby moves upwardly a cylindrical plunger 6 mounted so as to be moved up and down inside of a nozzle block 1 against the elastic force of a coil spring 7 provided on the top end of the plunger 6, and slightly opens a valve 8 and discharges the gelatinizer to form a thin film of the gelatinizer on the lower end of the valve 8. After that, this method throws a seed 9 into a passage 6a of above-mentioned plunger 6 and makes above-mentioned thin film hold the seed 9 and then further pressurizes the inside of above-mentioned gel accommodating portion 3 to raise the internal pressure of the space 5, and thereupon above-mentioned valve 8 is greatly opened and a great amount of gelatinizer is discharged and the gelatinizer wraps the seed 9 in it in cooperation with above-mentioned film, and when a grain-shaped gel-coated seed 9a is formed thereby, the gel-coated seed 9a is dropped due to its own weight into an lower hardening tank, not shown, containing a hardening agent. The gel part of the gel-coated seed 9a is hardened while being conveyed through the hardening tank, and the hardening agent is washed away in a water-washing portion to form a product.
However, such a double-cylinder nozzle method has a disadvantage that in case of gel-coating a heavy seed such as corn, bean and the like, it cannot be gel-coated in some cases because above-mentioned thin film of the gelatinizer is broken by the shock of dropping of the seed. In order to prevent the break of the thin film, it is conceivable to raise the viscosity of the gelatinizer, but a problem has occurred that since the gel coating layer is made harder by doing so, the seed is difficult to germinate. Moreover, there has been a problem that in case of gel-coating a seed having a poor germinating ability, it is necessary to make the viscosity of the gelatinizer as low as possible in order to obtain a sufficiently high germinating ability, but in a double-cylinder nozzle method a spreadable viscosity of the thin film has the lower limit which has sometimes made a gel-coating process impossible. Furthermore, when above-mentioned gel-coated seed 9a is dropped due to its own weight into a lower hardening tank, a hardening agent spattered onto the lower end of above-mentioned nozzle block 1 has sometimes made a gel-coating process impossible.
Next, a mold method is a method which throws a seed into a mold whose inner face is spherical and at the same time fills the mold with a gelatinizer and a hardening agent, and takes out the gel-coated seed from the mold after it has been hardened. In this case, since this method does not use a stretched thin film of a gelatinizer to support a seed differently from above-mentioned double-cylinder nozzle method, it has an advantage that the gelatinizer does not need to be made higher in viscosity in order to enforce the seed supporting ability and its viscosity can be freely set to an adequate degree to provide a high efficiency of germination. However, there has been a problem that since a gelatinizer is difficult to be released from a mold, a seed cannot be coated in the shape of a sphere in some cases, and in the worst case a gel-coated seed cannot be released from the mold. Further, there has been a problem that this method is disadvantageous in work efficiency due to necessity of an operation of removing a hardening agent or a gelatinizer stuck to a mold each time a gel-coating process is performed.
The present invention provides a gel coating method obtained by improving above-mentioned mold method, which gel coating method injects a gelatinizer and an object to be sealed into a mold having both a gelatinizer impermeability or a slight gelatinizer impermeability and a hardening agent permeability, allows a hardening agent to permeate throughout the mold by immersing the mold in the hardening agent, and uniformly hardens the gelatinizer, which is around above-mentioned object to be sealed, from its contacting part with the mold, and thereby renders the object to be sealed easily removable as a gel-coated object from the mold. This method can securely coat with gel even a heavy object to be sealed or an object to be sealed having a poor germinating ability since it does not support an object to be sealed with a thin film of a gelatinizer. Moreover, since hardening of a gelatinizer proceeds in order from the contacting part with a mold, no unhardened gelatinizer is stuck to the inner face of the mold and the mold releasability of a gel-coated object is remarkably improved in comparison with a conventional mold method, and it is possible also to suppress remaining of a gelatinizer in a mold.
Moreover, since a thin hardened layer of a gelatinizer is formed beforehand at a contacting part between a gelatinizer and a mold by making above-mentioned mold retain the hardening agent through immersing the mold in the hardening agent and taking out the mold before injecting the gelatinizer and an object to be sealed into the mold, it is possible to further improve a gel-coated object in mold releasability.
The inner face of a mold used in above-mentioned method is composed of a semispherical portion projecting downward and a cylindrical portion set upright on the spherical portion, and the whole depth from the top end of the cylindrical portion to the bottom end of the semispherical portion is made equal to or greater than the diameter of above-mentioned semispherical portion, and therefore a gel-coated object can be surely made sphere-shaped.
Further, in case of using a mold having a slight gelatinizer impermeability as above-mentioned mold, since one that is composed such that it takes a time of one or more seconds for a gelatinizer to permeate through the mold, it is possible to completely prevent the gelatinizer injected into the mold from leaking out before immersing the mold in a hardening agent.
Moreover, it is acceptable also to use a mold made of an elastic material as above-mentioned mold, transform the mold by pressing its lower part from below, and extrude a gel-coated object in the mold into the hardening agent, and then restore the mold to its original shape, and in this case it is possible to more quickly release the gel-coated object from the mold by the mechanical extrusion in addition to above-mentioned hardening.
And, this method limits the thickness of a hardened layer formed by reaction of a gelatinizer injected into above-mentioned mold upon the hardening agent retained beforehand in the mold to 20% or less of the radius of a semispherical portion forming the lower part of the mold and projecting downward. Therefore, since the gel-coated object proceeds in globing by a surface tension as suspending in the hardening agent, it is possible to make the gel-coated object more completely sphere-shaped.
And the present invention provides a gel coating apparatus suitable for using the gel coating method. That is, a gel coating apparatus according to the present invention comprises a mold which has both a gelatinizer impermeability or a slight gelatinizer impermeability and a hardening agent permeability, an object to be sealed feeding means for throwing a specific number of objects to be sealed into the mold, a gelatinizer feeding means for discharging an adequate amount of gelatinizer for applying to the object to be sealed, a hardening tank which is disposed below the gelatinizer feeding means and the object to be sealed feeding means and is filled with a hardening agent, a mold immersing means which can consecutively immerse molds in the hardening tank and take out the molds from the tank, and a gel-coated object collecting means for taking out a gel-coated object which is released from the mold and suspends in the hardening agent from the hardening tank, which gel coating apparatus immerses the mold having a gelatinizer and an object to be sealed injected in it by the object to be sealed feeding means and the gelatinizer feeding means in a hardening agent inside the hardening tank and thereby makes the hardening agent permeate throughout the mold to harden the surface of the gelatinizer in the mold and releases the gel-coated object from the mold.
According to this apparatus composition, a gelatinizer and an object to be sealed are injected into a mold respectively by an object to be sealed feeding means and a gelatinizer feeding means, and the mold is immersed in a hardening tank and is taken out from the tank, and at this time, since the gelatinizer in the mold starts to be hardened uniformly from the contacting part with the mold by the hardening agent which has permeated throughout the mold, the gel-coated object is easily released from the mold and is collected by a gel-coated object collecting means. Since this apparatus does not have a structure which holds an object to be sealed with a thin film of a gelatinizer, it can surely gel-coat even a heavy object to be sealed or an object to be sealed having a poor germinating ability, and further since hardening of a gelatinizer proceeds in order from the contacting part with the mold, no unhardened gelatinizer is stuck to the inner face of the mold and the mold releasability of a gel-coated object is remarkably improved and the remaining of a gelatinizer in the mold can be also suppressed.
The gel-coated collecting means comprises two pulleys arranged in the longitudinal direction, a belt wound around the pulleys, and a plurality of paddles stood upright on the outer face of the belt, and the paddles are moved in the hardening tank as one body with the belt by rotation of the pulleys to generate a circulating flow, transfer gel-coated objects suspending in the liquid surface, and scoop up and discharge a gel-coated object transferred to the terminal to the outside. According to this composition, since generation of a circulating flow for transferring gel-coated objects suspending and discharge of gel-coated objects which have been hardened can be performed by a single means having a simple structure, it is possible to attain manufacturing cost reduction and space saving by reduction of the number of devices.
And the mold immersing means comprises an upper pulley arranged near the gelatinizer feeding means and the object to be sealed feeding means and near the liquid surface of the hardening agent in the hardening tank, a lower pulley arranged distantly from the upper pulley and deeply in the hardening agent, and a mold built-in belt wound around the upper and lower pulleys, and the mold built-in belt has a plurality of molds whose openings face outward embedded in it. According to this composition, since it is possible to consecutively perform a gel coating process, the efficiency of work can be remarkably improved.